Heart valves are sometimes damaged by disease or by aging, resulting in problems with the proper functioning of the valve. Heart valve replacement has become a routine surgical procedure for patients suffering from valve dysfunctions. Traditional open surgery inflicts significant patient trauma and discomfort, requires extensive recuperation times, and may result in life-threatening complications.
To address these concerns, efforts have been made to perform cardiac valve replacements using minimally-invasive techniques. In these methods, laparoscopic instruments are employed to make small openings through the patient's ribs to provide access to the heart. While considerable effort has been devoted to such techniques, widespread acceptance has been limited by the clinician's ability to access only certain regions of the heart using laparoscopic instruments.
Still other efforts have been focused upon percutaneous transcatheter (or transluminal) delivery of replacement cardiac valves to solve the problems presented by traditional open surgery and minimally-invasive surgical methods. In such methods, a valve prosthesis is compacted for delivery in a catheter and then advanced, for example through an opening in the femoral artery, and through the descending aorta to the heart, where the prosthesis is then deployed in the valve annulus (e.g., the aortic valve annulus).
Various types and configurations of prosthetic heart valves are available for percutaneous valve replacement procedures. In general, prosthetic heart valve designs attempt to replicate the function of the valve being replaced and thus will include valve leaflet-like structures. Valve prostheses are generally formed by attaching a bioprosthetic valve to a frame made of a wire or a network of wires. Such a valve prosthesis can be contracted radially to introduce the valve prosthesis into the body of the patient percutaneously through a catheter. The valve prosthesis can be deployed by radially expanding it once positioned at the desired target site.
In addition to the delivery device itself, typical transcatheter heart implantation techniques entail the use of a separate introducer device to establish a portal to the patient's vasculature (e.g., femoral artery) and through which the prosthetic valve-loaded delivery device is inserted. The introducer device generally includes a relatively short sheath and a valve structure. By inserting the prosthetic heart valve-loaded sheath through the introducer valve and sheath, a low friction hemostasis seal is created around the outer surface of the delivery sheath. While highly desirable, friction between the introducer device and the delivery sheath can be problematic, leading to unexpected movement of the prosthesis prior to release from the delivery device. If the deployed prosthesis is incorrectly positioned relative to the native annulus, serious complication may arise including paravalvular leakage (PVL) or the requirement for placement of a permanent pacemaker.
For example, FIG. 1A illustrates, in simplified form, an introducer device 10 establishing a portal to a patient's vasculature 12, and through which a prosthetic heart valve-loaded delivery shaft 14 has been inserted. As shown, delivery shaft 14 has been manipulated to locate the loaded prosthetic heart valve 16 (generally referenced) near a desired position relative to an aortic valve 18. An outer delivery sheath 20 contains the prosthetic heart valve 16. However, it is not always possible to accurately position the delivery device containing the prosthetic heart valve 16 at the desired position. Accordingly, adjustments in the position must be made. Conventionally, adjusting the position of the prosthetic heart valve 16 is accomplished by moving handle 22 proximally or distally. In the example of FIG. 1B, handle 22 is moved proximally. However, as handle 22 is moved proximally, outer delivery sheath 20 pulls towards the inner wall of the descending aorta 29 and away from outer wall of aortic arch 28. With this movement, handle 22 has moved, but prosthetic heart valve 16 has not moved relative to aortic valve 18. Thus, it takes more movement of handle 22 to move prosthetic heart valve 22. Further, the location of prosthetic heart valve 16 often needs to be adjusted a very small amount, which is difficult to accomplish by pushing or pulling handle 22.
Accordingly, there is a need for an improved adjustment mechanism and method to more accurately position a prosthetic heart valve implanted via transcatheter delivery devices and methods.